d/README.Endless: Update downstream changes documentation

The issue with the commit sizes metadata has been resolved now. I was
able to convince upstream that the change could be made as it seemed
that we were the only consumers of it in eos-updater.

https://phabricator.endlessm.com/T18171

debian/README.Endless

@@ -12,14 +12,8 @@ status of things.
 Ways in which the Endless package differs from Debian:
  1. We don’t use the full OSTree grub integration (etc/grub.d/15_ostree,
  usr/libexec/libostree/grub2-15_ostree). (See T18848.)
- 2. We carry some custom patches which change the repository format to
- store extra data about commit sizes, which was used a long time ago in
- the client update UI. (See T17367.)
- 3. We re-enable gjs build dependency as we have a way to install/test it
- 4. We bring back trivial-httpd subcommand
+ 2. We re-enable gjs build dependency as we have a way to install/test it
+ 3. We bring back trivial-httpd subcommand
 
-#1, #3 and #4 can be fixed at some point in the future (especially #3 and #4
-if debian decides to re-add the support).
-However #2 cannot be entirely fixed, since we will always need some
-compatibility code for generating the additional metadata on the server side.
-However, it could potentially be moved out of the OSTree package (T17367).
+These can be fixed at some point in the future (especially #2 and #3 if
+debian decides to re-add the support).